Like other genes of eukaryotes, the genetic information comprising the genome of an avian retrovirus, the provirus, is expressed by transcription of chromosomal DNA into RNA which is then processed, transported from the nucleus to the cytoplasm and translated into polypeptides. The proposed studies are designed to delineate the pathway of retrovirus-specific RNA production in infected cells. Since the synthesis and processing of viral RNAs are apparently accomplished by normal cellular enzymes, these studies may provide insights into the pathway of messenger RNA production in eukaryotes. Employing molecular hybridization procedures developed for this purpose, newly synthesized virus-specific RNAs will be identified and purified. The kinetics of appearance of potential precursors and intermediates as well as the mature RNAs will be determined in pulse-chase studies. Purified RNAs will be analyzed by nucleic acid hybridization and sequencing and techniques and by oligonucleotide fingerprinting to characterize and locate the sites at which viral RNA synthesis is initiated and processing occurs. If the synthesis of virus-specific RNA is initiated outside of the provirus, the resulting precursor molecule should contain recognition sites for processing enyzmes and it might contain sequence elements involved in regulating viral RNA synthesis.